This invention relates to an automated vehicle system and more particularly to such a system including a safety drive prevention mechanism.
Automated storage and retrieval systems of the type presently known in the art are generally rack structures which include a plurality of lanes and a number of aisles which extend orthogonally from each lane. Items being stored in the rack, such as loaded pallets, are positioned in the aisles. To retrieve a loaded pallet from a position within an aisle or to deposit a loaded pallet therein, it is necessary for a vehicle, commonly referred to as a robot or satellite vehicle, to enter the aisle. Because robots are expensive it is been found advantageous to have a single robot service a number of the aisles which extend from a lane rather than to provide a robot for each aisle. To carry the robot between the various aisles, a vehicle commonly referred to as a transfer vehicle, or a transfer car or crane, which moves along the lane, is provided.
As is well known in the art, such transfer cars ride on tracks in the lanes. Generally, the lane structures are not open but the area between the tracks of the lane is a surface which functions as a walk path. This walk path is provided for any one of a number of reasons including, for example, to permit the visual inspection of pallets in the aisles to be accomplished or so that repair work on the robot or the transfer vehicle may be performed.
Because, as is well known in the art, the robots which are carried by the vehicles must leave the vehicles and enter the aisles, and because alignment of the robots with the tracks of the aisles is a relatively difficult procedure, the width of the transfer vehicle is generally made such that the sides of the transfer vehicle are close to the entrances of the aisles, thereby minimizing the distance the robots must move off the transfer vehicle before entering the aisle and thus simplifying the alignment of the robot with the aisle. Similarly, transfer vehicles are conventionally constructed so that the clearance between the bottom of the transfer vehicle and the walk path surface of the lane is minimal. This is because rack structures, for purposes of space use efficiency, are generally built several levels high. Clearly, minimizing the overall height of each transfer vehicle and robot, so that their combined vertical height approaches that required by a loaded pallet, permits the provision of a maximum number of vertically extending storage spaces in a minimum height.
These efficiencies, however, also result in a warehouse system in which the transfer vehicle utilizes virtually all the area of a lane and a person in a lane cannot stand to one side or lie down between the tracks to avoid being struck by a transfer vehicle which is moving in a line. Clearly, persons could easily by seriously injured if they are struck by the transfer cars which frequently exceed speeds of 400 ft. per minute while traveling in a lane.
It is to avoid the aforementioned problems that a number of different safety systems have been developed. One such prior art system involves the provision of emergency stop buttons mounted in the fore and aft sections of the transfer vehicle. These button switches, however, do not provide a satisfactory solution to the problem for a number of reasons. For one thing, it is necessary for a person in a lane to reach over the leading edge of the transfer vehicle to depress the switch and, because the vehicle is frequently traveling at speeds exceeding 400 ft. per minute, the person attempting to reach the switch may easily be struck by the vehicle while the attempt is being made. Additionally, the switch which is frequently a depression actuated button, presents such a small target that a person in the lane frequently cannot reach the button from the side or, in haste, can easily miss it completely. Another improved system which has been provided includes a pivotable bar located near the bottom portion of the transfer vehicle. The bar stretches across the width of the transfer vehicle and is arranged to pivot inwardly toward the vehicle to actuate an off-switch upon striking an object and being urged inwardly. This improved bar safety mechanism serves a two-fold purpose. Firstly, it prevents damage to the transfer vehicle in the event that an obstruction such as, for example, a section of wooden pallet is on the walk path between the tracks. Further, a person on the walk path can, in the event that it is noted that a transfer vehicle is bearing down, kick at the transversly extending bar, thereby actuating the emergency stop mechanism. It has been found, however, that notwithstanding the fact that the bar actuated mechanism is an improvement over the depression button mechanism discussed above, even the low bar mechanism is not completely satisfactory. This is because the bar mechanism requires a person on the walk path to lash out with his foot, thereby placing himself off-balance, and he is more readily subject to being knocked down by the vehicle while off-balance. Additionally, it is difficult for a person in a lane to reach the bar (which, as noted above, is located across the width of the transfer vehicle in the lower portion thereof) if the person is at the side of a lane rather than in the center thereof, and it is virtually impossible to reach the shut-off bar if the person is in the upper area of the lane.